This work focuses on the development of computational methods for predicting product stereoselectivities for catalytic asymmetric procedures using quantum mechanics (QM) and quantum mechanics/molecular mechanics (QM/MM). These methods will be used for designing highly selective asymmetric catalysts. The performance of these computationally derived catalysts will be assessed through experiment. Specifically, this work will examine enamine based stereoselective reactions catalyzed by organic molecules. Examples include aldol reactions, Mannich-type reactions, Michael reactions, Stetter reactions, and benzoin condensations. A specific thrust of this work will be to understand and explain, mechanistically, how thiazolium salts catalyzes the benzoin condensation and related transformations. Since the first proposed mechanism of the benzoin condensation by Breslow et al. in 1958, a number of other reaction pathways have been proposed and the true mechanism of this reaction is still debatable. These preliminary findings will form the basis for future efforts directed towards understanding the chemistry of thiazolium salts in biological systems. [unreadable] [unreadable]